U.S. patent application number 13/897400 was filed with the patent office on 2013-10-24 for turbine for an exhaust turbocharger of an internal combustion engine.
The applicant listed for this patent is DAIMLER AG. Invention is credited to Torsten Hirth, Siegfried Sumser.
Application Number | 20130276444 13/897400 |
Document ID | / |
Family ID | 44897688 |
Filed Date | 2013-10-24 |
United States Patent
Application |
20130276444 |
Kind Code |
A1 |
Hirth; Torsten ; et
al. |
October 24, 2013 |
TURBINE FOR AN EXHAUST TURBOCHARGER OF AN INTERNAL COMBUSTION
ENGINE
Abstract
In a turbine for an exhaust gas turbocharger of an internal
combustion engine having a housing part which has a receiving
chamber and which comprises a spiral duct through which exhaust gas
of the internal combustion engine can flow, the spiral duct having
an outlet cross-section via which exhaust gas is directed onto a
turbine wheel disposed in the receiving chamber whereby the turbine
wheel can be rotated, at least one flow control member is provided
which can be moved in the circumferential direction of the
receiving chamber and by means of which the flow cross-section can
be adjusted, wherein a warp angle of the outer contour region of
the wall over which the flow cross-section can be adjusted is
smaller than a wrap angle over which the outer contour region
thereof extends.
Inventors: |
Hirth; Torsten; (Ruthesheim,
DE) ; Sumser; Siegfried; (Stuttgart, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAIMLER AG |
Stuttgart |
|
DE |
|
|
Family ID: |
44897688 |
Appl. No.: |
13/897400 |
Filed: |
May 18, 2013 |
Current U.S.
Class: |
60/605.1 |
Current CPC
Class: |
F05D 2220/40 20130101;
F01D 17/167 20130101; F02C 7/00 20130101; F01D 17/141 20130101 |
Class at
Publication: |
60/605.1 |
International
Class: |
F02C 7/00 20060101
F02C007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 18, 2010 |
DE |
2010 051 777.1 |
Claims
1. A turbine (54) for an exhaust turbocharger (22) of an internal
combustion engine (10) having at least one housing part (56) with a
receiving chamber (94) and comprising at least one spiral duct (58)
through which exhaust gas from the internal combustion engine (10)
is conducted, said spiral duct (58) having an outlet cross-section
(A.sub.ZS) via which a turbine wheel (60), which is accommodated in
the receiving chamber (94) of the turbine housing (56) can be acted
on by the exhaust gas, and at a flow control member (68) which is
movable in the circumferential direction (70) of the receiving
chamber (94) and by means of which the outlet flow cross-section
(A.sub.ZS) to the turbine wheel (60) can be adjusted, the turbine
housing including a wall (96, 98), which delimits the spiral duct
(58) in the housing part (56) and an outer contour region (104)
which faces towards the flow control member (68) in the radial
direction (102) of the receiving chamber (94), said outer contour
region (104) having a counterpart contour which at least
substantially corresponds to an outer contour region (108), which
faces towards the outer contour region of the wall (96, 98) in the
radial direction (102) of the flow control member (68), by means of
which counterpart contour the outer contour area (108) of the flow
control member (68) can be covered at least in regions in the
radial direction (102), the outer contour region (108) of the flow
control member (68) having a wrap angle (.phi..sub.AB,ZS), over
which the outer contour region (108) thereof extends over the
circumference of the receiving chamber (94) in the circumferential
direction (70) thereof, and is smaller than a wrap angle
(.phi..sub.AB,TS) of the outer contour region (104) of the wall
(96, 98), over which the outer contour region (104) thereof extends
over the circumference of the receiving chamber (94) in the
circumferential direction (70) thereof.
2. The turbine (54) according to claim 1, wherein the turbine (54)
comprises another collector housing (72), which has at least one
inlet opening (76) and which has another receiving chamber (74),
which can be exposed to exhaust gas via the inlet opening (76), in
which the first housing part is accommodated, and which is fluid
connected to the spiral duct (58) to enable the exhaust to flow
from the other receiving chamber (74) into the spiral duct
(58).
3. The turbine (54) according to claim 1, wherein the housing part
(56) including the spiral duct (58) comprises at least another
spiral duct (58) through which exhaust of the internal combustion
engine (10) can flow, said spiral duct having an outlet
cross-section (A.sub.ZS) via which the turbine wheel (60)
accommodated in the receiving chamber (94) can be acted on by the
exhaust.
4. The turbine (54) according to claim 3, wherein the outlet
cross-section (A.sub.ZS) is configured such that it narrows, from
the outside to the inside, in the radial direction (102) of the
receiving chamber (94).
5. The turbine (54) according to claim 1, wherein a relative total
blocking V of the turbine (54) is expressed by: V = N TS .times.
.phi. AB , ZS 2 .times. .pi. , ##EQU00002## wherein: V is the
relative total blocking of the turbine (54), N.sub.TS is the number
of spiral ducts (58) that the housing part (56) comprises,
.phi..sub.AB,ZS is the wrap angle (.phi..sub.AB,ZS) of the outer
contour region (108) of the flow control member (68), and .pi. is
the circle constant, and wherein V is at least substantially less
than 0.35.
6. The turbine (54) according to claim 1, wherein a wrap angle
(.phi..sub.L,Zunge) of the flow control member (68), over which the
latter extends at least substantially in the radial direction (70)
of the receiving chamber (94), is larger than the wrap angle
(.phi..sub.AB,TS) of the outer contour region (104) of the wall
(96, 98).
7. The turbine (54) according to claim 1, wherein an angle
(.alpha..sub.Se) of at least substantially 45 degrees is bounded by
a first tangent (138) on a wall region (114) facing towards the
receiving chamber (94) in the radial direction (102) thereof, which
wall region delimits a spiral inlet cross-section (A.sub.TS) of the
spiral duct (58) on one side, which is delimited on the other side
by a wall region (116) facing away from the receiving chamber (94)
in the radial direction thereof (102), and by another tangent (140)
on a circle (106') outer-circumferentially tangentially
circumscribing the wall (96, 98) delimiting the spiral channel
(58), on which tangent an intersection point (142) with the first
tangent (138) also lies within the circumscribed circle (106').
8. The turbine (54) according to claim 1, wherein the outer contour
regions (104, 108) are each configured in the form as circular
segments.
Description
[0001] This is a Continuation-In-Part application of pending
international patent application PCT/EP2011/005308 filed Oct. 21,
2011 and claiming the priority of German patent application 10 2010
051 777.1 filed Nov. 18, 2010.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a turbine for an exhaust
turbocharger of an internal combustion engine, which includes a
turbine housing with a spiral duct via which exchanges is directed
onto a turbine wheel and a blocking.
[0003] DE 100 48 237 A1 discloses an internal combustion engine
with an exhaust turbocharger and an exhaust gas recirculation
device, wherein the turbocharger comprises an exhaust turbine
equipped with a variable turbine geometry in the exhaust tract and
a compressor in the intake tract of the internal combustion engine,
and wherein the exhaust gas recirculation device comprises a
recirculation line between the exhaust tract and the intake tract
and an adjustable check valve. The internal combustion engine
further comprises a control mechanism in which control signals can
be generated for adjusting the variable turbine geometry and the
check valve depending on the operating status of the internal
combustion engine.
[0004] The exhaust turbine is configured as a dual flow turbine
with two separate inflow channels to the turbine wheel, each
channel having an inlet cross-section, wherein the two inflow
channels are shielded from one another in a pressure-tight manner.
At least one inflow cross-section of an inflow channel to the
turbine wheel is alterable by means of the variable turbine
geometry. Provision is made of two separate exhaust lines in the
exhaust tract, each line connecting a part of the cylinder head
outlets of the internal combustion engine to each inflow channel.
The recirculation line of the exhaust recirculation device connects
exactly one of the two exhaust lines to the intake tract.
[0005] DE 25 39 711 discloses a spiral housing for an exhaust
turbocharger with a cross-section that is adjustable at least in
regions, wherein on the radially inner wall of the spiral housing
at least one sliding tongue is provided so as to be movable with
respect to this inner wall in the circumferential direction.
[0006] DE 10 2008 039 085 A1 discloses an internal combustion
engine for a vehicle with an exhaust turbocharger, which comprises
a compressor in an intake tract of the internal combustion engine
and a turbine in an exhaust tract of the internal combustion
engine. The turbine has a turbine housing, which comprises a spiral
duct coupled to an exhaust line of the exhaust tract and a turbine
wheel, which is arranged inside a receiving chamber of the turbine
housing and which can be acted on by exhaust gas from the internal
combustion engine fed through the spiral duct for driving a
compressor wheel of the compressor. The compressor wheel is
connected by a shaft to the turbine wheel for conjoint rotation.
The turbine comprises an adjustment mechanism with which a spiral
inlet cross-section of the spiral duct and also a nozzle
cross-section of the spiral duct leading to the receiving chamber
are jointly adjustable.
[0007] Because such exhaust turbochargers are a mass-produced
article with a continuously increasing number of parts in the
context of series production of internal combustion engines, it is
desirable to provide an exhaust turbocharger which provides for
efficient (i.e., low fuel consumption and low emission) operation
of the associated internal combustion engine and which also has
high operational reliability with extreme temperature and pressure
changes.
[0008] It is the object of the invention is thus to provide a
turbine for an exhaust gas turbocharger that has high operational
reliability and that also enables efficient operation of an
internal combustion engine associated with the exhaust
turbocharger.
SUMMARY OF THE INVENTION
[0009] In a turbine for an exhaust gas turbocharger of an internal
combustion engine having a housing part which has a receiving
chamber and which comprises a spiral duct through which exhaust gas
of the internal combustion engine can flow, the spiral duct having
an outlet cross-section via which exhaust gas is directed onto a
turbine wheel disposed in the receiving chamber whereby the turbine
wheel can be rotated, at least one flow control member is provided
which can be moved in the circumferential direction of the
receiving chamber and by means of which the flow cross-section can
be adjusted, wherein a warp angle of the outer contour region of
the wall over which the flow cross-section can be adjusted is
smaller than a wrap angle over which the outer contour region
thereof extends.
[0010] Such a turbine for an exhaust turbocharger of an internal
combustion engine comprises at least one housing part forming at
least one spiral duct through which exhaust from the internal
combustion engine can flow and which has an outlet cross-section
via which a turbine wheel, which is to be accommodated at least in
regions in the receiving chamber, of the turbine can be acted on by
the exhaust gas. The turbine further comprises at least one
blocking body which can be moved, in particular slid, at least
substantially in the circumferential direction of the receiving
chamber and by means of which the outlet cross-section can be
adjusted. To this end, a wall, which delimits the spiral duct at
least in regions, of the housing part has an outer contour region
which faces towards the blocking body in the radial direction of
the receiving chamber, said outer contour region being configured
as a counterpart contour corresponding at least substantially to an
outer contour region, which faces towards the outer contour region
of the wall of the receiving chamber in the radial direction, of
the blocking body, by means of which counterpart contour the outer
contour region of the blocking body can be covered at least in
regions in the radial direction, in particular towards the
outside.
[0011] According to the invention provision is made such that a
wrap angle, over which the outer contour region of the blocking
body extends in the circumferential direction of the receiving
chamber is smaller than a wrap angle, over which the outer contour
region of the wall extends in the circumferential direction of the
receiving chamber, of the outer contour region of the wall. In
other words, the angular range over which the outer contour region
of the blocking body extends is smaller than the angular range over
which the outer contour region of the wall relative to which the
blocking body can be moved extends. An adjustment range, especially
in an upper throughput range of the turbine, of the blocking body
is thus created in which the blocking body is covered in regions or
optionally also entirely by the wall in the radial direction,
especially towards the outside. The blocking body is configured,
for example, in the form of a tongue bypass and is therefore
designated as a tongue bypass, which has a tongue tip. The tongue
can be covered in regions, or optionally entirely, by the wall
and/or by the outer contour region thereof up to the tongue tip in
the radial direction.
[0012] In spite of this covering, with appropriate configuration of
the spiral duct (in particular surfaces of the spiral duct), the
blocking body can still define a narrowest flow cross-section of
said spiral duct, in particular the narrowest outlet cross-section
thereof.
[0013] The turbine of the invention thus has a particularly high
throughput range and a particularly high throughput spread angle
such that the turbine can be operated in a particularly efficient
manner and, in particular as a result of the movability of the
blocking body and in turn as a result of the adaptability of the
outlet cross-section associated therewith, the turbine can be
adapted to a plurality of different and dynamically changing
operating points of the internal combustion engine. The result is
an especially efficient, low fuel consumption operation, with low
CO.sub.2 emissions, of the internal combustion engine.
[0014] Furthermore, the variable turbine of the invention (which is
designated as a variable bypass turbine when the blocking body is
configured as a tongue-shaped bypass) is not only highly efficient
but is also simpler in design and has a small number of parts, in
particular compared to variable blade turbines. Thus low costs for
the turbine of the invention and high operational reliability go
hand in hand. In spite of its relatively simple design, the turbine
of the invention has the desired throughput spread angle, wherein
the quotient
.PHI. max .PHI. min > 3 ##EQU00001##
or in some cases even >4. In this throughput the spread angle
quotient, .phi..sub.max represents the maximum possible throughput
of the turbine and .phi..sub.min represents the minimum possible
throughput of the turbine.
[0015] The continuous tightening of emission limits, in particular
for nitrous oxide and soot emissions, is having considerable impact
on exhaust turbochargers for charging internal combustion engines.
Hence there are high demands in terms of supplying exhaust
turbochargers with charging pressure owing to high EGR (EGR=exhaust
gas recirculation) rates that must be achieved in medium load
ranges to full load ranges of internal combustion engines. Hence it
is necessary to provide a geometrically small turbine in terms of
dimensions or proportions for such an exhaust turbocharger, wherein
the required high turbine performances are achieved by increasing
the ram capacity or by reducing the swallowing capacity of the
turbine associated with the internal combustion engine.
[0016] Furthermore, an inlet pressure level of the turbine may be
raised by the counter-pressure of an exhaust cleaning device, in
particular a soot filter, arranged in the flow direction of the
exhaust downstream of the turbine, which requires further reduction
of the dimensions or proportions of the turbine. This goes hand in
hand with the problem that such size reductions generally also
reduce efficiency. However, this is necessary in order to satisfy
performance requirements of a compressor side of the exhaust
turbocharger for providing a desired air-exhaust supply, and in
turn for attaining desired torques or desired performances, as well
as lower emissions, of the internal combustion engine.
[0017] A turbine with the features of the invention can be designed
small in terms of its dimensions or proportions and still attain
the desired ram performance. High EGR rates are thus achievable. In
other words, an especially large volume of exhaust from an exhaust
side of the internal combustion engine associated with the turbine
can be recirculated to the air side thereof and fed into the intake
air of the internal combustion engine, thus lowering the emissions,
in particular the nitrous oxide and soot emissions, of the internal
combustion engine.
[0018] Owing in particular to its efficient adaptability to
different operating points of the internal combustion engine, the
turbine of the invention also enables operation optimized for
efficiency. The turbine of the invention is thus a variable turbine
that can be especially well adapted to various operating points of
the internal combustion engine. Decisive factors for the high
achievable throughput spread angle and the efficiency
characteristics of the turbine are the configuration and/or
specification of main dimensions of the wall or walls fixed
relative to the turbine housing and delimiting the spiral duct, and
also the configuration and/or specification of the blocking body,
in particular the tongue, said blocking body being arranged
downstream of and capable of moving relative to the turbine
housing. The simple basic function of the blocking body is the
definition (i.e., the delimitation at least in regions) of the
narrowest flow cross-section of the spiral duct over as much of the
entire adjustment range, in particular the angle adjustment range,
of the blocking body as possible in the circumferential direction
of the receiving chamber over the circumference thereof, wherein
the blocking body is moved over the entire adjustment range by
means of, say, an actuator.
[0019] The turbine of the invention enables the narrowest flow
cross-section, in particular the narrowest outlet cross-section of
the spiral duct leading to the receiving chamber to be delimited in
regions, in particular at a tip of the blocking body on the one
hand and in regions by an area of a fixed wall of the turbine
housing on the other hand, wherein the wall region faces towards
the receiving chamber. This is advantageously achieved in the main,
particularly in the entire adjustment range of the blocking body.
This means that the narrowest flow cross-section is not completely
defined, i.e., delimited, in the adjustment range (or else only in
a small area of the adjustment range) by walls of the spiral duct
fixed relative to the turbine housing and forming the spiral
duct.
[0020] If the narrowest flow cross-section were delimited in an
undesirably large area of the adjustment range of the blocking body
by walls fixed relative to the turbine housing (rather than at
least in regions by the blocking body), this would mean that beyond
a certain position (in particular an adjustment angle) of the
blocking body in the adjustment range, a further movement of said
blocking body would have no influence on a change of the current
throughput of the turbine. In other words, a further movement of
the blocking body beyond this specific position would not lead to a
desired increase of the throughput. With the turbine of the
invention, this problem is avoided such that a movement of the
blocking body from one position, in particular an adjustment angle,
to a different position relative thereto, in particular an
adjustment angle, at least substantially always has an impact on a
change of the throughput of the turbine. As a result the turbine of
the invention has a particularly high throughput spread angle and
can be adapted to different and dynamically changing operating
points of the internal combustion engine in a particularly flexible
manner. This is particularly advantageous when the turbine is used
in a car, as internal combustion engines and thus turbines perform
in a particularly transient manner in cars.
[0021] In the field of turbo-charging an internal combustion engine
for a car, the turbine of the invention thus ensures a pleasant and
advantageous driving performance, even for an internal combustion
engine configured according to the so-called downsizing principle,
wherein the internal combustion engine has a relatively small
piston displacement but relatively high performances and torques.
Obviously the turbine of the invention is also suitable for use in
commercial vehicles.
[0022] In a particularly advantageous embodiment of the invention,
the turbine comprises an additional housing part having at least
one inlet opening, which housing part has another receiving chamber
which can be exposed to exhaust via the intake opening and in which
the first housing part is accommodated and wherein said chamber is
fluidly connected to the spiral duct in order to enable a flow of
the exhaust from the receiving chamber into the spiral duct. With
this additional housing part, exhaust can initially collect in the
receiving chamber for a ram induction drive of the turbine and thus
of the internal combustion engine associated therewith. The turbine
is thus able to satisfy the previously described high performance
demands on the compressor side of the exhaust turbocharger. In the
receiving chamber functioning as a collection chamber, the exhaust
can collect and build up in pressure before flowing through the at
least one spiral duct and driving the turbine wheel. The turbine
wheel is connected to a shaft for conjoint rotation, to which shaft
a compressor wheel of a compressor of the exhaust turbocharger is
likewise connected for conjoint rotation.
[0023] The first housing part is advantageously an element
configured separately from the second housing part and inserted in
the other housing part as an inset. The turbine of the invention
can thus be economically manufactured and assembled.
[0024] In another advantageous embodiment of the invention, the
housing part comprising the at least one spiral duct (i.e., the
first housing part) comprises at least one other spiral duct
through which exhaust from the internal combustion engine can flow,
which other spiral duct has an outlet cross-section via which the
turbine wheel accommodated in the receiving chamber can be acted on
by the exhaust gas. Through both of these at least two spiral
ducts, a plurality of segments is presented via which the turbine
wheel can be acted on by the exhaust in an efficient manner. This
contributes towards the high efficiency and smooth operation of the
turbine of the invention.
[0025] A corresponding blocking body can also be allocated to the
outlet cross-section of the other spiral duct, which blocking body
can be moved in the circumferential direction of the receiving
chamber over the circumference thereof and by means of which
blocking body the outlet cross-section of the other spiral duct can
be variably adjusted. Here too provision can advantageously be made
such that a wall, which delimits the other spiral duct at least in
regions, of the housing part has an outer contour region facing
towards the other blocking body in the radial direction of the
receiving chamber, which outer contour region is configured as a
counterpart contour corresponding at least substantially to an
outer contour region of the other blocking body facing towards the
outer contour region of the wall of the other spiral duct in the
radial direction of the receiving chamber, by means of which
counterpart contour the outer contour region of the other blocking
body can be covered at least in regions in the radial direction and
in particular towards the outside. The wrap angle of the outer
contour region of the other blocking body is also advantageously
configured smaller than the wrap angle of the outer contour region
of the wall of the other spiral duct. The previously described
advantages are thus also achievable for the housing part with the
at least two spiral ducts.
[0026] When the housing part of this embodiment of the invention
with the at least two spiral ducts is arranged in the other
receiving chamber of the other housing part, the at least two
spiral ducts will be supplied with exhaust gas from the common
receiving chamber. In other words, the receiving chamber is divided
into the at least two spiral ducts in the flow direction of the
exhaust gas from the inlet opening of the receiving chamber to the
turbine wheel downstream of the inlet opening, thereby providing a
particularly advantageous and efficient incident flow to the
turbine wheel. Furthermore, the turbine with the housing part
having the at least two spiral ducts can also be operated in the
ram induction mode, with the advantages associated therewith.
[0027] In another advantageous embodiment of the invention, the
outlet cross-section is configured so that it narrows in the radial
direction of the receiving chamber, in particular from the outside
to the inside. In other words, the outlet cross-section narrows in
the radial direction towards a rotation axis of the turbine wheel.
A particularly large throughput spread angle is thus achieved in
the turbine of the invention. This measure also results in a
minimization of an absolute radial blocking of the outlet
cross-section by the blocking body, wherein a wrap angle of the
outer contour region of the blocking body is kept small in relation
to the wrap angle of the outer contour region of the wall.
[0028] To determine an at least substantially optimum number
N.sub.TS of spiral ducts, which are also designated as partial
spirals, of the housing part, emphasis is advantageously placed on
a radial blocking of the blocking body directly correlated with the
wrap angle of the wall of the blocking body. In doing so it is
advantageous to maintain a relative total blocking V, which is
expressed as
V=N.sub.TS.times..phi..sub.AB,ZS/(2.times..pi.)
[Note: some of the letter designations in the mathematical formulas
and expressions are derived from the original German terms.] and
which is at least substantially less than 35% (0.35). The relative
total blocking V is given by the number N.sub.TS of spiral ducts of
the housing part and the wrap angle .phi..sub.AB,ZS of the outer
contour region of the blocking body, as well as by the constant
.pi. multiplied by two. A relative total blocking V clearly less
than 35% is particularly advantageous.
[0029] In another particularly advantageous embodiment of the
invention, a reduction of the efficiency of the turbine of the
invention, particularly in an uppermost throughput range thereof,
can be brought about by adjustment of a so-called trip edge or
interference edge for the flow of the exhaust. The turbine of the
invention exhibits very high levels of efficiency, especially up to
and including upper throughput ranges, wherein the trip edge or
interfering edge and the accompanying efficiency reduction for
limiting the rotational speed of the turbine represents a
substantial point in connection with very good controllability of
the turbine and improves the controllability of the turbine of the
invention.
[0030] A wrap angle of the blocking body, over which the blocking
body extends at least substantially in the circumferential
direction of the receiving chamber over the circumference thereof,
is advantageously configured larger than the wrap angle of the
outer contour region of the wall. In other words, the relationship
of the wrap angle .phi..sub.L,Zunge of the blocking body
(Zunge=tongue) to the wrap angle .phi..sub.AB,TS of the outer
contour region of the wall is expressed as follows:
.phi..sub.L,Zunge>.phi..sub.AB,TS.
[0031] In at least virtually the entire adjustment range of the
blocking body, it is thus possible to achieve a complete opening
position in which the maximum outlet cross-section is represented,
even with the trip edge or interfering edge situated where the
blocking body and/or outer contour region of the blocking body is
covered by the wall and/or the outer contour region of the wall and
still opening transversely.
[0032] The adjustability of a maximum realizable cross-sectional
area of the spiral duct or of the outlet cross-section by means of
the blocking body serves as a means for influencing a maximum
throughput capacity of the turbine of the invention. Along with the
appropriate design of the blocking body, this maximum
cross-sectional area or the maximum outlet cross-section is also
substantially determined by the appropriate design of the spiral
duct and in particular the wall, which faces towards the blocking
body in the radial direction of the receiving chamber, of the
spiral duct.
[0033] A key parameter of the design of the spiral duct is the
angle of the wall, which faces in the radial direction of the
receiving chamber towards the receiving chamber or the blocking
body, of the spiral duct, which wall delimits the spiral duct in
the circumferential direction. In order to achieve a high
throughput capacity of the turbine, this angle is advantageously
configured with the greatest possible values, especially in an
upper adjustment range of the tongue bypass (blocking body) in
order to maximize the cross-sectional area or the outlet
cross-section in the opening position of the tongue bypass.
[0034] In an advantageous embodiment of the invention, an angle of
at least substantially 45.degree. is bounded by a first tangent on
a wall facing towards the receiving chamber in the radial direction
thereof, by which a spiral inlet cross-section of the spiral duct
is delimited on one side, which is delimited on the other side by a
wall facing away from the receiving chamber in the radial direction
thereof, and by another tangent on a circle outer-circumferentially
tangentially circumscribing the wall delimiting the spiral duct, on
which tangent an intersection point with the first tangent lies
within the circumscribed circle. This gives rise to an entry angle
of the flow of the exhaust gas into the spiral duct of at least
substantially 45.degree., which angle can be configured at least
substantially constant in the flow direction downstream along the
wall.
[0035] When the first housing part is accommodated in the other
housing part, the other housing part (which is also the one
providing the receiving chamber) is configured such that a flow
angle of the flow of the exhaust at least substantially corresponds
to this entry angle. The other housing part is optionally
configured such that a larger flow angle thereto is formed in order
that the other housing part may be used for other first housing
parts configured as, e.g., insets that enable, e.g., a higher
throughput. In summary, the wall, which faces towards the blocking
body in the radial direction and delimits the blocking channel
towards the circumferential direction, of the spiral duct can bound
an angle of at least substantially 45.degree., wherein this angle
can be configured as constant in the flow direction and in the
wall. However, this angle may also vary in the flow direction of
the exhaust along the wall.
[0036] For configuring this angle progression from the opening
position to a closing position of the blocking body, in which
dosing position a minimum flow cross-section, in particular a
minimal outlet cross-section is set, it is advantageous to have an
angle progression from a high value to a low value relative thereto
on the surface of the spiral duct, i.e., on the surface of the wall
delimiting the spiral duct. In the range of the dosing position of
the blocking body, surface angles of the wall in a range of, e.g.,
10.degree. to 20.degree. inclusive with respect to the
circumferential direction are favorable values, which lead to
advantageous levels of efficiency and an advantageous ram induction
performance of the turbine.
[0037] In another embodiment of the invention, provision can be
made such that the housing part has at least two spiral ducts,
wherein the spiral ducts are configured asymmetric relative to one
another. Because the spiral ducts are not configured identical to
one another, blade excitations of the turbine wheel caused by wakes
over the perimeter of the turbine wheel can be influenced
differently and curbed. The spiral channels differ from one another
in terms of, for example, their division ratio.
[0038] In another embodiment of the invention, the outer contour
regions are each configured in the form of arcs, in particular as
circular segments. This measure keeps the manufacturing costs down
and likewise renders the blocking body very easy to adjust, for
example by pivoting it about a rotation axis. If the outer contour
regions are configured as circular segments, their respective
center points are then advantageously situated on the rotation axis
of the turbine wheel, about which axis the blocking body also
pivots for the variable adjustment of the outlet cross-section. For
example, provision is thus made such that the outer contour region
of the blocking body is configured concave and the outer contour
region of the wall is configured convex.
[0039] Other advantages, features, and details of the invention
will emerge from the following description of preferred examples of
embodiment and by referring to the drawing. The following features
and combinations of features mentioned in the description and/or
the features and combinations of features shown only in the figures
can not only be used in these particular combinations, but also in
other combinations or alone without exceeding the scope of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] It is shown is in:
[0041] FIG. 1 a schematic diagram of an internal combustion engine,
which is charged by means of an exhaust turbocharger comprising a
multi-segment bypass turbine, which enables the operation of the
internal combustion engine in the ram induction mode;
[0042] FIG. 2 a schematic cross-sectional view of the multi-segment
bypass turbine according to FIG. 1;
[0043] FIG. 3 a schematic cross-sectional view in sections of
another embodiment of the multi-segment bypass turbine according to
FIG. 2;
[0044] FIG. 4 a schematic cross-sectional view in sections of
another embodiment of the multi-segment bypass turbine according to
FIG. 3;
[0045] FIG. 5 a diagram representing a throughput progression of
multi-segment bypass turbine according to FIGS. 3 and 4 over an
adjustment angle range of the bypass (blocking body); and
[0046] FIG. 6 a diagram representing a progression of the level of
efficacy of the multi-segment bypass turbine according to FIG. 5
over an adjustment angle range of the bypass.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0047] FIG. 1 shows an internal combustion engine 10 with six
cylinders 12. During the operation of the internal combustion
engine 10, air is taken in as indicated by the directional arrow 14
and filtered through an air filter 16 and flows in the direction
indicated by the arrow 18 into a compressor 20 of a turbocharger 22
associated with the internal combustion engine 10. The air is
compressed by the compressor 20 by means of a compressor wheel 24,
causing it to heat up. To cool the air thus compressed and thus
heated, said air flows in the direction indicated by the arrows 26
to a charge air cooler 28 and further in the direction indicated by
the arrows 30 to an air collector 32, via which it is fed in the
direction indicated by the arrows 34 to the cylinders 12. In the
cylinders 12, the intake and compressed air is exposed to fuel and
combusted, bringing about a rotation of a crankshaft 36 of the
internal combustion engine 10 in the direction indicated by the
arrow 38. Hence the internal combustion engine 10 is a direct
injection internal combustion engine such as a gasoline engine, a
diesel engine, or a Diesel-Otto (DiesOtto) engine. What has been
described thus far and what shall be described in the following,
however, is also readily transferrable and applicable to other
kinds of internal combustion engines, e.g., engines with manifold
injection.
[0048] The compressor 20 arranged on an air side 40 of the internal
combustion engine 10 serves to provide a desired air supply to the
internal combustion engine 10 for achieving a desired performance
or torque level of the internal combustion engine 10. The internal
combustion engine 10 can thus have a compact design in terms of its
piston displacement volume and thus in terms of its dimensions,
which goes hand in hand with light weight, high specific
performance, low fuel consumption, and low CO.sub.2 emissions.
[0049] Exhaust of the internal combustion engine 10 produced from
the combustion in the cylinders 12 is conducted via exhaust lines
42 to an exhaust side 44 of the internal combustion engine,
initially to an exhaust recirculation device 45 by means of which
exhaust from the internal combustion engine 10 can be recirculated
from the exhaust gas side 44 to the air side 40. To this end, the
exhaust recirculation device 45 comprises an exhaust recirculation
valve 46 by means of which a specified quantity of exhaust to be
recirculated can be set, said quantity of exhaust being adapted to
an existing operating point of the internal combustion engine 10.
The exhaust flows in the direction indicated by an arrow 52 to an
exhaust recirculation cooler 50, which cools the exhaust before it
is fed in the direction indicated by the arrow 48 into the intake
air by the internal combustion engine 10. This exposure of the
intake air to the recirculated exhaust leads to a reduction of
emissions, especially of nitrous oxide and particle emissions of
the internal combustion engine 10 such that the latter not only
exhibits low fuel consumption and high performance but also low
emissions.
[0050] Furthermore, the exhaust can be conducted by means of the
exhaust lines 42 to a turbine 54 of the exhaust turbocharger 22,
said turbine 54 being configured as a so-called single flow
multi-segment bypass turbine, which is explained with reference to
FIG. 2. The turbine 54 comprises a first housing part 56, which has
three spiral ducts 58 through which exhaust from the internal
combustion engine 10 flows. The spiral ducts 58 have respective
spiral inlet cross-sections A.sub.S as well as nozzle
cross-sections A.sub.R. A turbine wheel 60, which is to be
accommodated in the housing part 56, of the turbine 54 is rotatable
about a rotation axis 62.
[0051] The exhaust of the internal combustion engine 10 now enters
the spiral ducts 58 via the respective spiral inlet cross-sections
A.sub.S and flows via the respective nozzle cross-sections A to the
turbine wheel 60, whereby the turbine wheel 60 is driven by the
exhaust and turns. The turbine wheel 60 is connected to a shaft 62'
of the exhaust turbocharger for conjoint rotation, to which shaft
the compressor wheel 24 is also connected for conjoint rotation,
whereby the compressor wheel 24 can be driven by the shaft 62' of
the turbine wheel 60.
[0052] The turbine 54 also comprises an adjustment mechanism 64,
which in turn comprises an adjustment ring 66 connected to three
blocking bodies in the form of tongue bypasses 68, one bypass 68
being allocated to each spiral duct 58. The adjustment ring 66 can
be turned in the direction indicated by the arrows 70 about the
rotation axis 62 of the turbine wheel 60, whereby the spiral inlet
cross-sections A.sub.S as well as the nozzle cross-sections A.sub.R
evenly spaced in the circumferential direction of the turbine wheel
60 around the circumference thereof can be adjusted. In other
words, this means that by turning the adjustment ring 66, the
bypasses 68 can be adjusted between at least one position that
narrows or even doses the nozzle cross-sections A.sub.R and at
least one position that unblocks the nozzle cross-sections A.sub.R.
A variability of the turbine 54 is thus enabled by the adjustment
ring 64, whereby the turbine 54 can be adapted to various operating
points in at least virtually the entire characteristic field of the
internal combustion engine 10, thus enabling the internal
combustion engine 10 to operate in an efficient manner with low
fuel consumption and low emissions. The ram induction performance
and/or the throughput performance of the turbine 54 can be variably
adjusted by adjusting the nozzle cross-sections A.sub.R
[0053] By means of the spiral ducts 58, which form a plurality of
segments of the turbine 54, the internal combustion engine 10 can
be operated in the ram induction mode. To enable the operation of
the internal combustion engine 10 in the ram induction mode, the
turbine 54 comprises a collector housing 72 with which a common
collection chamber 74 for the spiral ducts 58 is formed, which
chamber is sealed from the surroundings in a gas-tight manner by
the collector housing 72, wherein the collector housing 72 can
surround the housing part 56 on the sides of a bearing mechanism
and hence on a side facing towards the compressor wheel 24 and/or
on a side opposite this side, i.e., on the sides of a turbine
outlet. The collector housing 72 has an inlet duct 76 into which
exhaust can flow via the exhaust lines 42 in the direction
indicated by an arrow 78 and which conducts the exhaust into the
collection chamber 74. As can be discerned in FIG. 2, the inlet
duct 76 narrows in the flow direction of the exhaust indicated by
the arrow 78. The exhaust conducted via the inlet duct 76 into the
collection chamber 74 is first collected in the collection chamber
74 and can then flow through the spiral ducts 58 to the turbine
wheel 60. A mixing as well as a collection of the exhaust thus
takes place in the direction of the exhaust flow through the
exhaust lines 42 upstream of the housing part 56.
[0054] Upstream of the respective spiral outlet cross-sections
A.sub.S, the spiral ducts 58 each have an at least substantially
trumpet-shaped inlet duct 80, via which the exhaust can enter the
spiral ducts 58. The turbine 54 exhibits a high level of
variability, with which different ram induction performances and
thus different EGR rates are achievable. This also enables the
provision of a specific air supply to the internal combustion
engine 10 for satisfying high performance or high torque
requirements. The turbine 54 further comprises only a small number
of parts, which goes hand in hand with low costs and a high level
of operational reliability.
[0055] In principle it is also possible to produce dual flow
turbines along the lines of the embodiment of the turbine 54,
wherein another housing part with at least two spiral ducts in the
form of, for example, the housing part 56 is arranged along the
rotation axis 62 of the turbine wheel 60 next to the housing part
56, which other housing part is accommodated in another receiving
chamber similar to the receiving chamber 74 and formed by another
housing part similar to the collector housing 72. The collection
chambers are thus aligned parallel to one another and are separated
from one another in a gas-tight manner. In this case provision is
made of two housing parts 56 arranged parallel to one another,
which each have a certain blocking effect and, by means of, say, a
manifold part, also effect a certain ram-charging of the two
collection chambers, which are gas tight relative to one another,
for separate cylinder groups of the cylinders 12 of the internal
combustion engine 10. A variable quasi-dual flow turbine with an
adjustment mechanism on both sides similar to the adjustment
mechanism 64 and corresponding bypasses 68 is thus represented.
Depending on the intended use, an asymmetric ram induction
performance is also achievable with this turbine.
[0056] The adjustment mechanism 64 of the turbine 54 is controlled
or governed by a control mechanism 82 of the internal combustion
engine 10, which adjusts the adjustment mechanism 64 so as to adapt
the turbine 54 to a prevailing operating point of the internal
combustion engine 10.
[0057] After acting on and driving the turbine wheel 60, the
exhaust flows via the turbine outlet in the direction indicated by
the arrow 88 out of the turbine 54 and flows through an exhaust
after-treatment device 90, which comprises, for example, a
catalytic converter, in particular a nitrous oxide catalyst, and
optionally a particle filter, after which the cleaned exhaust is
discharged into the environment as indicated by the arrow 92.
[0058] FIG. 3 shows an alternative embodiment of the turbine 54
according to FIG. 2, wherein the turbine 54 according to FIG. 3 can
also be used with the internal combustion engine 10. In FIG. 3 the
turbine wheel 60 is shown highly schematically for a better
overview. The turbine wheel 60 of the turbine 54 according to FIG.
3 is likewise accommodated in a receiving chamber 94 of the housing
part 56 such that it is capable of rotating about the rotation axis
62 in a rotation direction indicated by the arrow 71.
[0059] FIG. 3 shows a spiral duct 58 of the housing 56 through
which duct the exhaust from the internal combustion engine 10 can
flow and via which the exhaust can flow into the receiving chamber
94 so that it can act on the turbine wheel 60. It is obvious that a
plurality of spiral ducts can be distributed similarly to the
control duct 58 in the circumferential direction of the turbine
wheel 60 over the circumference thereof, as indicated by the arrow
70, wherein the spiral ducts 58 can be configured identical, i.e.,
symmetric to one another or configured asymmetric to one
another.
[0060] As can be discerned in FIG. 3, the turbine 54 according to
FIG. 3 differs from the turbine 54 according to FIG. 2 in
particular in terms of the configuration of the walls 96 and 98
delimiting the spiral duct 58 and in terms of the configuration of
the flow control members 68. FIG. 4 shows a wrap angle .phi..sub.TS
over which the wall 96 and/or the walls 98 extends/extend in the
circumferential direction of the receiving chamber 94 over the
circumference thereof. FIG. 3 shows three different positions 1, 2,
and 3 of the flow control members 68, wherein different adjustment
angles .epsilon. are set for moving the bypasses 68 into different
positions such as positions 1, 2, and 3. For example, from a tip
100 of the wall 98, the adjustment angle .epsilon. of the bypasses
68 increases as the flow control member 68 rotates in the direction
of the rotation of the turbine wheel 60 indicated by the arrow
71.
[0061] The walls 96 and 98 delimiting the spiral duct 58 in regions
each have an outer contour region 104 facing towards the respective
flow control member 68 in the radial direction of the receiving
chamber indicated by the arrow 102, which contour region is at
least substantially configured in the form of a circular segment
and designated as a cylinder segment. This is the case where (as
shown in FIG. 3) a circle 106 tangent to the outer contour regions
104 can be circumscribed around a center point indicated by the
arrow 70 situated on the rotation axis 62. In other words, the
outer contour regions 104 are circular segments of the
circumscribed circle 106 with the center point situated on the
rotation axis 62. The outer contour regions 104 are configured
concave.
[0062] Similarly, the flow control members 68 each also have an
outer contour region 108 facing towards the respective outer
contour region 104 of the walls 96 and 98 in the radial direction
of the receiving chamber 94 as indicated by the arrow 102. The
outer contour regions 108 are also configured, at least
substantially, in the form of circular segments and are likewise
designated as cylinder segments. The outer contour regions 108 also
represent circular segments of the circumscribed circle 106. Hence
the outer contour regions 104 are configured as counterpart
contours that correspond to, and are in particular at least
substantially complementary to the respective outer contour regions
108, wherein the outer contour regions 108 of the flow control
members 68 can be covered, at least in regions, in the radial
direction indicated by the arrow 102 by said counterpart
contours.
[0063] FIG. 3 shows a wrap angle .phi..sub.AB,ZS of the outer
contour region 108 of the flow control members 68 and also a wrap
angle .phi..sub.AB,TS of the outer contour region 104 of the wall
96 (or 98). For a better overview the wrap angles .phi..sub.AB,ZS
and .phi..sub.AB,TS are illustrated with reference only to one of
the bypasses 68 and with reference only to the wall 96. Obviously
what is described with reference to the flow control member 68 and
with reference to the wall 96 applies similarly to the other flow
control member 68 and to the wall 98, as well as to other walls of
the housing part 56. The wrap angle .phi..sub.AB,ZS of the outer
contour region 108 is configured smaller than the wrap angle
.phi.AB,TS of the outer contour region 104 of the wall 96 (or 98),
thus giving rise to an adjustment angle range of the bypasses 68 in
an upper throughput range of the turbine 54, wherein the bypasses
68, which extend over a wrap angle .phi..sub.L,Zunge shown in FIG.
3 are covered partially or optionally entirely towards the outside
from a rear edge 110 to a tip 112 of the flow control member 68
partially or optionally entirely in the radial direction indicated
by the arrow 102 by the outer contour region 104 of the walls 96
and 98 fixed relative to the housing part 56 and to the housing
part 72, but are still able to determine, at least to a large
extent, the narrowest flow cross-section of the turbine 54 if the
surfaces and thus the outer contours of the walls are appropriately
configured.
[0064] It is advantageous if the narrowest flow cross-section of
the turbine 54 is defined by the flow control members 68, at least
in regions, over at least virtually the entire adjustment angle
range of the flow control members 68, over which range the flow
control members 68 can be moved from a first end position to
another end position. The narrowest flow cross-section should thus
be delimited, at least to a large extent, over the entire
adjustment angle range between the tip 112 of the movable bypasses
68 and the outer contour region 114 of the walls 96 and 98. The
outer contour region 114, which for a better overview is
illustrated only with reference to the wall 96 in FIG. 3, thus
delimits the outside of the spiral duct 58 in the radial direction
and faces in the radial direction towards the receiving chamber 94
or the flow control members 68, as opposed to an outer contour
region 116 of the wall 96 (or 98), which faces away from the
receiving chamber 94 or the flow control member 68.
[0065] With reference to both FIGS. 5 and 6, it can be discerned
that the bypasses 68 in position 1 give rise to at least virtually
the smallest throughput parameter .phi..sub.min in that they set at
least virtually the smallest flow cross-section A.sub.ZS,min
between their tips 112 and the outer contour region 114.
[0066] What is not desired is for the tip 100, which is immobile
relative to the housing part 56, to form the narrowest flow
cross-section of the turbine 54 beyond a certain adjustment angle
.epsilon. of the flow control members 68, whereby the throughput
spread angle of the turbine 54 or the function of the flow control
members 68 beyond this respective adjustment angle .epsilon. would
no longer have any effect on a desired throughput increase of the
turbine 54 if this adjustment angle .epsilon. were reduced any
further. In other words, if this respective adjustment angle
.epsilon. is situated in the adjustment angle range undesirably far
ahead of one of the end positions to which the flow control members
68 can be set for providing the largest flow cross-section, the
flow control members 68 can then be moved undesirably far from this
respective adjustment angle .epsilon. to the end position, and this
movement would no longer have an effect on a throughput increase
since the narrowest flow cross-section would then be formed by the
fixed walls 96 and 98. Such a flow cross-section is designated with
A.sub.TS in FIG. 3.
[0067] The turbine 54 of FIG. 3 enables the narrowest flow
cross-section of the turbine 54 to be delimited in regions at least
virtually in the entire adjustment angle range of the flow control
members 68 or allows the adjustment angle .epsilon. from which the
narrowest flow cross-section of the turbine 54 is formed by the
fixed walls 96 and 98 to be situated particularly dose to the end
position of the flow control member 68, wherein the end position
is, for example, the position 3 shown in FIG. 3 in which the
smallest possible adjustment angle .epsilon. of the flow control
members 68 is set.
This can also be discerned by referring to FIGS. 5 and 6. FIG. 5
shows a diagram 118 in which the adjustment angle .epsilon. of the
flow control members 68 is plotted on the abscissa 120 and in which
the throughput parameter .phi. is plotted on the ordinate 122. The
throughput parameter .phi. is calculated from the mass flow of the
exhaust flowing through the turbine 54 and from the temperature
T.sub.3l and the pressure p.sub.3l in the flow direction of the
exhaust ahead of (upstream of) the turbine, wherein the turbine
pressure ratio .pi..sub.t-s is constant.
[0068] Moving the flow control members 68 over their entire
adjustment angle range .epsilon..sub.ges from one end position into
the other end position gives rise to the progression 124 of the
throughput parameter .phi. illustrated in diagram 118. The maximum
possible and settable throughput parameter .phi..sub.max and the
smallest possible throughput parameter .phi..sub.min of the turbine
54 are shown in diagram 118. One of these end positions of the flow
control members 68 is position 3, in which a negative adjustment
angle .epsilon. is set relative to the tip 100 of the wall 98. As
follows from diagram 118, the maximum throughput parameter
.phi..sub.min is situated especially close to and ahead of (end)
position 3 when the latter is set. As can also be inferred from
FIG. 5, the smallest possible throughput parameter .phi..sub.min
can be set by moving the flow control members 68 into the other end
position, wherein the smallest possible throughput parameter
.phi..sub.min is still situated within the adjustment angle range
.epsilon..sub.ges. This means that the throughput parameter .phi.
can be influenced in virtually the entire adjustment angle range
.epsilon..sub.ges, ideally in the entire adjustment angle range
.epsilon..sub.ges, by moving the flow control members 68. The
turbine 54 can thus be adapted especially well to different
operating points of the internal combustion engine 10.
[0069] As follows from FIG. 5, there is a relatively high level of
efficiency .eta..sub.t-s in position 1 of the flow control members
68, in which position at least virtually the smallest flow
cross-section A.sub.ZS,min is set. In position 2 of the flow
control members 68, in which a comparatively greater flow
cross-section A.sub.ZS is set, there is a comparatively higher
level of efficiency .eta..sub.t-s. In position 3 of the flow
control members 68, in which there is also a relatively large flow
cross-section compared to position 1, there is a lower level of
efficiency .eta..sub.t-s of the turbine 54 compared to positions 1
and 2.
[0070] FIG. 6 shows another diagram 126, in which the adjustment
angle range .epsilon. is plotted on the abscissa 128. The
efficiency .eta..sub.t-s of the turbine 54 is plotted on the
abscissa 130 of diagram 126. Adjusting the flow control members 68
in their adjustment angle range .epsilon..sub.gss gives rise to a
progression 132 of the efficiency .eta..sub.t-s. As in diagram 118,
positions 1, 2, and 3 of the bypasses 68 are also plotted in
diagram 126 and the associated throughput parameters .phi. or
efficiency levels .eta..sub.t-s can be discerned.
[0071] From position 2 of the flow control members 68 on, a further
increase of the throughput range can be effected by further
reduction of the adjustment angle .epsilon. if a movable or
adjustable ring nozzle 134 of the spiral duct 58 (or of the spiral
ducts 58) via which the exhaust flows into the receiving chamber 94
narrows in the radial direction indicated by the arrow 102 towards
the rotation axis 62, at least in terms of its width, i.e., its
extension in the circumferential direction of the receiving chamber
94 according to the arrow 70, over the circumference thereof.
[0072] The Flow control members 68 have, in relation to the
rotation direction indicated by the arrow 71, a rear edge 110
opposite the tip 112, which edge is also designated as a trip edge
or interference edge and which enables an efficiency reduction in
the uppermost throughput range beyond position 2 in the direction
of position 3. The turbine 54 configured as a bypass turbine
exhibits a high level of efficiency .eta..sub.t-s up into the upper
throughput range, wherein the edge 110 provides an efficiency
reduction representing a safety option for limiting the speed of
the turbine 54 and also represents a substantial point associated
with the excellent controllability of the turbine 54.
[0073] The relationship of the wrap angle .phi..sub.L,Zunge to the
wrap angle .phi..sub.AB,TS is expressed as follows:
.phi..sub.L,Zunge>.phi..sub.AB,TS.
[0074] It is thus possible to achieve a complete opening position
of the control members 68 (position 3) in at least virtually the
entire adjustment angle range .epsilon..sub.ges, even with the edge
110 situated where the control members 68 is covered by the wall 96
(or by the wall 98) and is still opening transversely (position
3).
[0075] If the adjustment angle .epsilon. is increased further past
position 1, the movable control members or the movable control
member 68 become(s) situated to an increasingly greater extent in
the outlet region of the spiral duct 58 (in the nozzle 134) and, as
a throttle element, lead(s) to a greater loss creation, wherein
there may be a slight increase in the turbine throughput capacity
with respect to the minimum throughput parameter .phi..sub.min due
to an unblocking of the cross-section in the direction of the
bypasses 68. In general the adjustment angle range here is limited
to the position of the minimum throughput parameter .phi..sub.min
for the option of a maximum possible pressure buildup of the
turbine 54.
[0076] As follows from the previous descriptions, the maximum
throughput capacity of the turbine 54 is influenced by setting the
maximum possible flow cross-section A.sub.ZS. Along with the
configuration of the control members 68, the flow cross-section
A.sub.ZS or the corresponding cross-sectional area is determined by
the configuration of the spiral ducts 58 and in particular by the
configuration of the outer contour region 114. A key parameter for
the configuration of the spiral duct 58 or spiral ducts 58 is an
angle .alpha..sub.S (shown in FIG. 3) of the outer contour region
114 of the wall 96 (or of the wall 98) delimiting the spiral duct
58 radially on the outside towards the circumferential direction
according to the arrow 70. In other words, the angle .alpha..sub.S
is the angle bounded by the outer contour region 114 or the
tangents thereon and by the circumscribed circle 106 or the
corresponding tangents on the circumscribed circle 106. In order to
achieve a particularly high throughput capacity of the turbine 54,
the angle .alpha..sub.S is advantageously configured with the
greatest possible values in the upper adjustment range of the
bypasses 68 in order to maximize the flow cross-section A.sub.ZS in
the opening position (position 3) of the flow control members
68.
[0077] FIG. 4 shows an entry angle .alpha..sub.Se, which is at
least substantially 45.degree.. The angle .alpha..sub.Se is bounded
by two tangents 138 and 140. The tangent 138 is a tangent on the
outer contour region 114 of the wall 96 by which the flow
cross-section A.sub.TS is delimited in regions and on one side. The
flow cross-section A.sub.TS is delimited on the other side by the
outer contour region 116 of the wall 98. The tangent 140 is a
tangent on a circumscribed circle 106', which is concentric to the
circumscribed circle 106 and which tangentially surrounds the wall
96 on the outer perimeter in the radial direction. A point of
intersection 142 of the tangent 138 with the circumscribed circle
106' lies on the tangent 140.
[0078] From this angle .alpha..sub.Se and continuing in the flow
direction of the exhaust through the spiral channel 58 indicated by
a directional arrow 144 along the outer contour region 114 of the
wall 96, the entry angle .alpha..sub.Se (which can also be other
than a 45.degree. angle) remains at least substantially constant,
whereas it varies in the wall 96 according to FIG. 4.
[0079] The housing part 72 surrounding the spiral ducts 58 is
advantageously configured and dimensioned such that a flow angle of
the exhaust at least substantially corresponds to the entry angle
.alpha..sub.Se or optionally larger flow angles of the exhaust are
achieved in order that housing parts 56 with greater throughput may
be used with the collector housing 72.
[0080] For configuring the progression of the angle .alpha..sub.S
from the entry angle .alpha..sub.Se of the opening position of the
flow control members 68 to the closing position, on the outer
contour region 114 it is advantageous to have an angle progression
from a high value to a low value in the flow direction of the
exhaust, as can be discerned from the outer contour region 114
according to FIG. 4. In the range of position 1 (the dosing
position) of the bypasses 68, angles .alpha..sub.S of the outer
contour region 114 ranging from, e.g., 10.degree. to 20.degree.
inclusive in the circumferential direction result in favorable
efficiency (.eta..sub.t-s) of the turbine 54.
* * * * *